Conventionally, to diagnose or to predict into the future a degree of progress of diseases, analyses are performed by using medical images. For example, to diagnose Alzheimer's disease (Alzheimer-type dementia), atrophy of the brain caused by progress of the disease is evaluated by performing an analysis while using images acquired with Magnetic Resonance Imaging (MRI). More specifically, according to a known technique for evaluating atrophy of the brain, the region of the brain is detected from an MRI image obtained by imaging the head of an examined subject (hereinafter “patient”), and the volume of the detected brain is measured. Further, for example, according to a known technique (called Voxel-based Morphology) for evaluating the degree of atrophy, an image of the brain of a patient is positioned so as to be aligned with a standard image of the brain (a standard brain). However, to perform these types of analyses accurately, it is necessary to detect the brain and align the position thereof in a precise manner.